JP4892230B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a light source including a green phosphor having high luminance and small luminance change due to temperature as a backlight.

  The liquid crystal display device includes a backlight unit 1 and a liquid crystal element 2 as shown in an exploded perspective view of FIG. The backlight unit 1 includes a light source 5 and a drive circuit 9 (inverter) for lighting the light source 5, a housing 3, a reflection plate 4, a diffusion plate 6, a prism sheet 7, and a polarization reflection plate 8.

  In the liquid crystal display device, the light from the light source 5 is guided to the liquid crystal element side by the backlight unit, the light transmission amount of the liquid crystal element 2 is adjusted for each pixel, and red, green, and blue for each pixel. Color display is performed by spectroscopically transmitting any light.

In general the liquid crystal display device light source, a cold cathode fluorescent tube (CCFL: C old C athode F luorescent L amp) is used. FIG. 9 shows a cross-sectional view of the CCFL in the long axis direction. The CCFL has a structure in which a phosphor 12 is applied to the inner wall of a glass tube 11 and electrodes 13 are provided at both ends of the tube. Further, mercury Hg and a rare gas (argon Ar or neon Ne) are sealed as a discharge medium 14 in the tube.

  The CCFL used for this type of backlight (synonymous with a light source) has a very long and characteristic shape unlike a fluorescent lamp for indoor illumination. In general, fluorescent lamps for indoor lighting have a tube diameter (tube inner diameter) of about 30 mm and a tube length of about 1100 mm. On the other hand, in the CCFL, for example, in the case of a 32-inch liquid crystal display device, the tube diameter (tube inner diameter) is about 4 mm and the tube length is about 720 mm. CCFL is characterized by a very small tube diameter.

  In such a CCFL, lighting is performed by applying a high voltage to the electrodes 13 at both ends. When voltage is applied, electrons emitted from the electrode excite mercury Hg, and ultraviolet light is emitted when the excited mercury Hg returns to the ground state. The phosphor is excited by the ultraviolet rays and emits visible light to the outside of the tube.

  The phosphor 12 provided in the CCFL includes a blue phosphor whose emission color is blue (main emission peak wavelength is about 400 nm to 500 nm) and a green phosphor whose main emission peak wavelength is about 500 nm to 600 nm. And a red phosphor powder having a red color (with a main emission peak wavelength of about 600 nm to 650 nm) are mixed to form a predetermined white chromaticity.

In general, blue phosphor BaMgAl ₁₀ O ₁₇ : Eu ²⁺ , green phosphor LaPO ₄ : Tb ³⁺ , Ce ³⁺ , and red phosphor Y ₂ O ₃ : Eu ³⁺ are used as these three color phosphors. ing. In addition, as a general notation of the phosphor material, the front of “:” indicates the matrix material composition, the back indicates the emission center, and means that some atoms of the matrix material are replaced with the emission center. For example, in the green phosphor LaPO ₄ : Tb ³⁺ , Ce ³⁺ , LaPO ₄ is a base material, and a part of lanthanum La is substituted with terbium Tb, which is the emission center. Cerium Ce is added as a sensitizer that sensitizes the emission of Tb. Therefore, LaPO ₄ : Tb ³⁺ , Ce ³⁺ may be described as (La, Tb, Ce) PO ₄ .

  As shown in FIG. 8, the visible light emitted from the CCFL (light source 5) is transmitted through optical members such as a diffusion plate 6, a prism sheet 7, and a polarization reflection plate 8 disposed immediately above the backlight unit 1. Is incident on the liquid crystal element 2 facing the surface. Further, in order to improve the utilization efficiency of light from the CCFL, the reflecting plate 4 is disposed immediately below the CCFL, and the light reflected by the reflecting plate is transmitted through the optical member described above and is incident on the liquid crystal element 2.

  On the other hand, the liquid crystal element 2 has a cross-sectional structure shown in FIG. That is, a pair of glass substrates 21 (21A, 21B) facing each other and an alignment film 23 are applied on the inner surface of each substrate, and further, a liquid crystal 24 and a color filter 25 (red 25A, green 25B, blue) are interposed between the substrates. 25C) is a sandwiched structure.

  The glass substrate 21 (21A-21B) is held by a spacer 26. The polarizing plates 22 (22A, 22B) are respectively disposed outside the pair of substrates 21 (21A, 21B). The liquid crystal 24 is uniformly aligned by the alignment film 23 and is driven by applying a voltage to an electrode group (not shown in FIG. 13) formed for each pixel. When a voltage is applied, the liquid crystal rotates according to the electric field generated thereby, and the refractive index of the liquid crystal layer changes to adjust the light transmission amount.

  The color filter 25 (25A, 25B, 25C) splits the white light W from the backlight unit 1 into red light R, green light G, and blue light B for each pixel, and transmits any light. There are various display modes depending on the initial alignment of the liquid crystal and the driving thereof.

Representative display modes, there are IPS (I n P lane- S witching ) mode, VA (V ertically A ligned) mode, OCB (O ptically C ompensated B end) mode, TN (T wisted N ematic) mode .

  In particular, at present, IPS mode and VA mode are mainstream in large-sized liquid crystal televisions. In the IPS mode, liquid crystal molecules aligned substantially parallel to the substrate surface are driven by an electric field substantially horizontal to the substrate surface. On the other hand, the VA mode is a system in which liquid crystal molecules aligned substantially perpendicular to the substrate surface are driven by an electric field substantially perpendicular to the substrate surface. Both modes have excellent viewing angle characteristics and are suitable for large liquid crystal display devices.

  In this way, the liquid crystal display device adjusts the amount of light transmitted from the light source provided in the backlight unit for each pixel with the liquid crystal element, and transmits any one of red, green, and blue light for each pixel. Color display is performed by spectrally dividing with a color filter.

Incidentally, this kind of green phosphor LaPO _4: Tb ^3+, as the literature on Ce ^3+, for example, Patent Documents 1-7 and Non-Patent Document 1 are given below.

JP-A-57-23684, JP-A-4-338105, JP-A-5-302082 JP-A-6-56412, JP-A-9-249879, JP 2000-109826 A, JP 2002-212553 A, Journal of Chemical Physics Vol. 60, No. 2, p. 34 (1974) {The Journal of Chemical Physics, Vol. 60, No. 1, p34 (1974)}

  In recent years, the market for liquid crystal display devices is mainly expanding as a large-sized liquid crystal television, and further cost reduction and higher image quality are required. In order to solve these demands, it is a challenge to increase the brightness of CCFL, which is a light source, and to make the luminance and chromaticity distribution uniform.

  In particular, increasing the brightness of CCFLs is an important issue. By solving this problem, it is possible to reduce the cost of a liquid crystal display device. For example, when designing a backlight unit having the same brightness, the number of CCFLs can be reduced as compared with the prior art, and considering that the number of inverters can be reduced at the same time, a great reduction in cost can be realized. Further, by increasing the brightness of the CCFL, it is possible to omit an optical member (for example, a brightness enhancement film) interposed between the CCFL and the liquid crystal element, so that the cost of the liquid crystal display device can be reduced.

  On the other hand, the luminance and chromaticity distribution of CCFL is a factor that greatly affects the image quality of a liquid crystal display device, and its uniformity is an important issue. In a liquid crystal display device, an amount of light transmitted from a light source is adjusted by a liquid crystal element, and further an image is displayed by performing spectroscopy, so that a human is looking directly at the light source through the liquid crystal element. Therefore, the luminance / chromaticity distribution characteristics of the CCFL directly affect the image quality of the liquid crystal display device. In particular, in the case of a long and thin tube such as CCFL, luminance / chromaticity distribution (spots) in the tube axis direction is likely to occur.

  In addition, when multiple CCFLs are arranged in the backlight unit, image quality degradation due to the difference in luminance and chromaticity between the CCFL arranged at the center of the backlight unit and the CCFL arranged at the end is also a problem. . It is necessary to improve the luminance distribution and chromaticity distribution of the light source in order to improve the image quality of liquid crystal display devices that are becoming larger.

  Note that the luminance distribution and chromaticity distribution, which are the subject, are made uniform to some extent by the thick film diffusion plate 6 disposed immediately above the CCFL. However, if the subject can be solved by the light source 5 alone, It is also possible to reduce the thickness. This leads to cost reduction of the liquid crystal display device.

  Therefore, in the present invention, for the purpose of achieving both low cost and high image quality of a liquid crystal display device that is increasing in size, the problem is to improve the luminance of a light source represented by CCFL and to make the luminance and chromaticity distribution uniform. These problems are solved by the means described in.

  The present invention solves the problems of increasing the brightness of a light source and uniforming the luminance and chromaticity distribution, and provides the following means for the purpose of providing a high-quality liquid crystal display device that achieves both low cost and high image quality. Use.

First, as a first means, a light source including a three-color light emitting phosphor of a blue phosphor whose emission color is blue, a green phosphor that is green, and a red phosphor that is red, and A liquid crystal display device comprising a liquid crystal element having a color filter that adjusts the amount of light transmitted from a light source for each pixel and transmits blue, green, or red light for each pixel. The phosphor is represented by the composition formula (La _1-xy , Tb _x , Ce _y ) PO ₄ , and the composition ratio x and y satisfy the following expressions (1) and (2), respectively. .

0.500 <x + y <0.700 (1)
1.20 <y / x <2.00 (2)
Furthermore, in consideration of the emission characteristics of ultraviolet rays that excite the phosphor described later, and the temperature characteristics of the phosphor, the green phosphor is represented by the composition formula (La _1-xy , Tb _x , Ce _y ) PO ₄ , It is preferable that the composition ratios x and y satisfy the following expressions (3) and (4), respectively.

0.500 <x + y <0.650 (3)
1.50 <y / x <1.70 (4)
In addition to the above means, the light source includes a sealed container including a three-color light emitting phosphor of a blue phosphor, a green phosphor, and a red phosphor, a discharge medium enclosed in the sealed container, and a voltage across the discharge medium. It is desirable that the phosphor is excited to emit light by a plurality of ultraviolet rays having different wavelengths emitted from the discharge medium.

  At this time, it is desirable that at least one of the plurality of ultraviolet rays having different wavelengths emitted from the discharge medium includes vacuum ultraviolet rays having a wavelength of less than 200 nm, and at least one includes ultraviolet rays having a wavelength of 200 nm or more.

  Specifically, the main component of the discharge medium is mercury Hg. Among the ultraviolet rays emitted from the discharge medium, one is a vacuum ultraviolet ray having a wavelength of 185 nm, and one is preferably an ultraviolet ray having a wavelength of 254 nm.

Furthermore, when the intensity ratio I ₁₈₅ / I ₂₅₄ between the vacuum ultraviolet ray having a wavelength of 185 nm and the ultraviolet ray having a wavelength of 254 nm is 0.20 or more in the sealed container, the effect of the phosphor composition ratio can be remarkably shown.

  The sealed container is a tubular glass tube, and the inner diameter of the tube is desirably 5 mm or less.

  At this time, the electrodes provided in the glass tube are disposed at both ends of the glass tube and disposed inside the glass tube, or disposed at both ends of the glass tube and disposed outside the glass tube. It is desirable that

  As one specific light source satisfying these conditions, the light source is preferably a cold cathode fluorescent tube having mercury Hg as a main component of the discharge medium and having an inner diameter of 5 mm or less.

The green phosphor described above preferably has a median particle size d _{50 in} the range of 3.0 μm to 6.0 μm.

  On the other hand, the liquid crystal element includes a pair of opposed transparent substrates, an alignment film applied on the inner surfaces of the pair of substrates, a liquid crystal layer sandwiched between the alignment films, and an outer main surface of the pair of substrates. The alignment film is a vertical alignment film, and the liquid crystal is aligned substantially perpendicular to the substrate surface when no voltage is applied, and transmits light by tilting with respect to the substrate surface when a voltage is applied. A configuration characterized by adjusting the amount is desirable.

  In the present invention, by using the above means, it is possible to achieve both the improvement of the luminance of the light source and the uniformization of the luminance / chromaticity distribution. Further, by using such a light source, it is possible to obtain a high-quality liquid crystal display device that achieves both low cost and high image quality in a liquid crystal display device that is increasing in size.

In the present invention, a blue phosphor whose emission color is blue (main emission peak wavelength of about 400 nm to 500 nm), a green phosphor whose main color is green (main emission peak wavelength of about 500 nm to 600 nm), and a red phosphor (main emission). A light source equipped with a three-color phosphor emitting a red phosphor having a peak wavelength of about 600 nm to 650 nm, and the amount of light transmitted from the light source is adjusted for each pixel, and either blue, green, or red is adjusted for each pixel. A liquid crystal display device having a color filter having a color filter that transmits the light, and the green phosphor is represented by a composition formula (La _1-xy , Tb _x , Ce _y ) PO ₄ , The composition ratios x and y satisfy the following expressions (1) and (2) simultaneously.

0.500 <x + y <0.700 (1)
1.20 <y / x <2.00 (2)
Furthermore, the composition ratios x and y satisfy the following expressions (3) and (4) at the same time.

0.500 <x + y <0.650 (3)
1.50 <y / x <1.70 (4)
The greatest feature of the present invention is that (La _1-xy , Tb _x , Ce _y ) PO ₄ is used as a green phosphor used as a light source constituting a backlight of a liquid crystal display device, and the composition ratio is expressed by the formula ( 1) and (2) are satisfied at the same time. Furthermore, the composition ratio satisfies the expressions (3) and (4) at the same time.

The present invention uses the green phosphor (La _1-xy , Tb _x , Ce _y ) PO ₄ having a new composition ratio to achieve two major problems relating to the light source of the liquid crystal display device described above: (1) high brightness and (2) Simultaneously solve the uniform luminance / chromaticity distribution.

(La _1-xy , Tb _x , Ce _y ) PO ₄ has the emission spectrum shown in FIG. 5 and is a material that has been used in conventional fluorescent lamps for indoor lighting. The composition ratio is greatly different. The composition ratio of (La _1-xy , Tbx, Cey) PO4 in the present invention is a composition ratio that can realize both high luminance and uniform luminance / chromaticity distribution when used as a light source of a liquid crystal display device.

  The inventors pay attention to the fact that the light source of the liquid crystal display device is greatly different from the fluorescent lamp for indoor lighting, and the composition ratios shown in the above formulas (1) and (2), and further the formulas (3) and ( It has been found that the composition ratio shown in 4) is effective for the light source of the liquid crystal display device.

In addition, the composition of the phosphor shown here is a basic composition and is not a description considering a very small amount of impurities. In general, when a phosphor is synthesized, a flux (melting material) is used, and after the synthesis, a flux constituent element may exist as a trace impurity. For example, when synthesizing (La _1-xy , Tb _x , Ce _y ) PO ₄ , lithium tetraborate Li ₂ B ₄ O ₇ may be used as a flux, and a small amount of lithium Li is present as a phosphor There is.

  In addition, when the phosphor is fired, the phosphor and the firing container (for example, an alumina crucible) are in contact with each other, so a trace amount of elements constituting the container may be present. The description in this specification is not a description considering a very small amount of impurities that do not affect the optical characteristics of the phosphor.

Hereinafter, in the present invention, the reason why the above composition ratio is effective for the light source of the liquid crystal display device will be described for each problem.
(1) Higher brightness CCFL used in liquid crystal display devices is characterized by a particularly small tube diameter, and is significantly different in structure (shape) from fluorescent lamps used for indoor lighting. For example, the tube diameter (inner tube diameter) is about 30 mm in the general household illumination fluorescent lamp, whereas it is as small as about 4 mm in the CCFL. The present inventors paid attention to the fact that this difference in tube diameter greatly affects the radiation characteristics of ultraviolet rays generated inside the CCFL, and the green phosphor (La _1-xy , Tb _x , optimal for the ultraviolet radiation characteristics). The composition ratio of Ce _y ) PO ₄ was found.

  CCFLs and illumination fluorescent lamps are classified as mercury lamps as light source classifications. That is, mercury is sealed as a discharge medium in a glass tube provided with a phosphor inside, and the phosphor is caused to emit light by ultraviolet rays emitted from the mercury.

The ultraviolet rays emitted from mercury, there are a plurality of ultraviolet light of different wavelengths, for example, wavelength of 365 nm, 313 nm, 298 nm, include 254 nm, further vacuum ultraviolet 185nm wavelength of less than 200nm (VUV: V acuum U ltra v iolet). The radiation ratio (intensity ratio) of these ultraviolet rays greatly depends on the tube diameter (inner diameter) and temperature of the glass tube, and the radiation ratio differs greatly between the illumination fluorescent lamp and the CCFL. Since the light emission characteristics of the phosphor are greatly influenced by the radiation characteristics of the ultraviolet light that is the excitation source, the optimum composition of the phosphor varies greatly depending on the radiation ratio of various ultraviolet light. The present invention focuses on this point.

  When the tube diameter is large like an illumination fluorescent lamp, ultraviolet rays having a wavelength of 254 nm are mainly emitted from mercury, and other ultraviolet rays are hardly emitted. Accordingly, the phosphor in the illumination fluorescent lamp is excited mainly by ultraviolet rays having a wavelength of 254 nm.

On the other hand, when the tube diameter is reduced, the radiation ratio of 185 nm vacuum ultraviolet light is increased. From the study by the present inventors, it was found that when the tube diameter is as small as 5 mm or less as in CCFL, the emission ratio I ₁₈₅ / I ₂₅₄ of the wavelength of 185 nm vacuum ultraviolet light and 254 nm ultraviolet light is 0.20 or more. . Furthermore, this radiation ratio also depends greatly on the temperature of the tube, and the radiation ratio I ₁₈₅ / I ₂₅₄ is 0.50 or more in a high-temperature environment (60 ° C or higher) where the CCFL is lit in the backlight unit. Cases are also conceivable.

  The phenomenon that the radiation ratio of the vacuum ultraviolet ray having a wavelength of 185 nm is high is a specific phenomenon in a light source having a very small tube diameter (tube inner diameter of 5 mm or less) like CCFL, and is greatly different from a fluorescent lamp for illumination. Therefore, the phosphor in the CCFL is excited by two types of ultraviolet rays having different wavelengths, that is, 254 nm ultraviolet rays and 185 nm vacuum ultraviolet rays.

Therefore, the present inventors pay attention to the 185 nm vacuum ultraviolet ray having a high radiation ratio in CCFL, and can achieve both the phosphor emission characteristic at the wavelength 254 nm ultraviolet excitation and the phosphor emission characteristic at the wavelength 185 nm vacuum ultraviolet excitation (La The composition ratio of _1-xy , Tb _x , Ce _y ) PO ₄ was studied. As a result, it has been found that the composition range shown in the formulas (1) and (2) is optimal for increasing the luminance of the light source for liquid crystal display devices. Furthermore, it has been found that the composition range shown in the formulas (3) and (4) is more optimal. Details of the optimum composition ratio of (La _1-xy , Tb _x , Ce _y ) PO ₄ will be described below.

In (La _1-xy , Tb _x , Ce _y ) PO ₄ , Tb is the emission center, and an emission spectrum as shown in FIG. 5 is shown by emission from Tb. And this light emission process changes with wavelengths of excitation ultraviolet rays. Ultraviolet light having a wavelength of 220 nm to 300 nm is absorbed by Ce and emits light by energy transfer from Ce to Tb.

  On the other hand, vacuum ultraviolet rays having a wavelength of 160 nm to 200 nm emit light by direct absorption by Tb. These technical contents are described in, for example, The Journal of Chemical Physics, Vol. 60, No. 1, p34 (1974). Therefore, when this phosphor is applied to CCFL, it is necessary to efficiently convert two types of ultraviolet rays (wavelength 185 nm vacuum ultraviolet rays and wavelength 254 nm ultraviolet rays) generated in the tube into visible light. The composition ratio of Tb is important. In particular, x + y (total amount of Ce + Tb) and y / x (ratio of Ce and Tb amount) are important.

Therefore, the present inventors evaluated the luminance of (La _1-xy , Tb _x , Ce _y ) PO ₄ having various composition ratios under vacuum ultraviolet excitation and 254 nm ultraviolet excitation. The evaluation results are shown in the graphs of FIGS. The brightness in this graph is expressed as a relative value, and the excitation of green phosphor (La _1-xy , Tb _x , Ce _y ) PO ₄ (x + y = 0.428, y / x = 2.18), which is currently widely used. The luminance is shown as 100%. The indication of VUV excitation in the figure represents vacuum ultraviolet excitation.

  This evaluation with vacuum ultraviolet excitation should be performed using vacuum ultraviolet light with a wavelength of 185 nm, but since there is no light source capable of emitting a single vacuum ultraviolet light with a wavelength of 185 nm, in this study, a xenon excimer light source with a wavelength close to the wavelength (172 nm wavelength) ) Was used. Although the wavelengths are different, since both are vacuum ultraviolet rays and the absorption band of the phosphor is the same, there is no problem even if the phosphor emission characteristics at 172 nm excitation are used in the discussion.

  From FIG. 2, it can be seen that the relative luminance in each excitation changes greatly by changing x + y (Ce + Tb amount). At this time, with 254 nm ultraviolet excitation, the luminance increases as x + y increases, and the relative luminance exceeds 100% when x + y = 0.42 or more.

  On the other hand, in the vacuum ultraviolet excitation (VUV excitation), a substantially parabolic change is shown, and the luminance is high in the range of 0.45 to 0.70. In CCFL, the light emission characteristics under 254 nm ultraviolet excitation and the light emission characteristics under vacuum ultraviolet excitation are observed as a combination of characteristics at a certain ratio. Therefore, considering the balance between the luminance at 254 nm ultraviolet excitation and the luminance at vacuum ultraviolet excitation, x + y is preferably in the range of 0.50 to 0.70. When x + y is 0.65 or more, the brightness of VUV excitation decreases, but the brightness at 254 nm excitation is very high, so it is possible to increase the brightness up to 0.70. Furthermore, since the effect can be detected visually if the relative luminance is 102% or more, x + y is preferably in the range of 0.50 to 0.65.

Next, the relationship between y / x (Ce / Tb ratio) and relative luminance was examined for (La _1-xy , Tb _x , Ce _y ) PO ₄ having a composition range in which high luminance can be expected. The result is shown in FIG. From FIG. 3, it can be seen that the relative luminance in each excitation changes greatly by changing y / x. The change in luminance at each excitation changes to a substantially parabolic shape with respect to y / x, and considering the compatibility between the luminance at 254 nm ultraviolet excitation and the luminance at vacuum ultraviolet excitation (VUV excitation), y / x is preferably in the range of 1.20 to 2.00. Furthermore, if both the relative luminances are 102% or more, the effect can be detected visually, so y / x is preferably in the range of 1.50 to 1.70.

For these reasons, a composition ratio that satisfies 0.500 <x + y <0.700 and 1.20 <y / x <2.00 at the same time is desirable for high brightness. Furthermore, a composition ratio that satisfies 0.500 <x + y <0.650 and 1.50 <y / x <1.70 at the same time is desirable.
(2) Uniformity of luminance / chromaticity distribution Another issue is the luminance / chromaticity distribution of the light source. In particular, in the case of CCFL, luminance / chromaticity distribution occurs in the tube axis direction, and this distribution affects the image quality of the liquid crystal display device. In a liquid crystal display device, an amount of light transmitted from a light source is adjusted by a liquid crystal element, and further an image is displayed by performing spectroscopy, so that a human is looking directly at the light source through the liquid crystal element. Therefore, in the liquid crystal display device, uniforming the luminance and chromaticity distribution of the light source is a very important issue. On the other hand, in the fluorescent lamp for illumination, such luminance / chromaticity distribution is not necessarily an important issue. In the case of an illumination fluorescent lamp, humans hardly see the light from the fluorescent lamp directly, and the reflected light irradiated to a certain object is seen. Therefore, the luminance / chromaticity distribution of the fluorescent lamp itself has little influence.

  The present invention pays attention to a problem different from that of a fluorescent lamp for illumination, that is, uniform luminance and chromaticity distribution necessary for a light source for a liquid crystal display device, and solves the problem.

  In the CCFL, the present inventors paid attention to the temperature characteristics of the phosphor as one factor causing the luminance / chromaticity distribution. The temperature characteristic described here refers to a phenomenon in which the luminous efficiency of the phosphor changes with temperature when an excitation source having the same intensity is irradiated onto the phosphor. FIG. 6 is a conceptual diagram for explaining the temperature characteristics of the phosphor. When the temperature characteristics are poor (corresponding to characteristics A and C in the figure), the change in luminous efficiency (luminance) is large with respect to the temperature change of the phosphor. That is, the inclination of the luminance change with respect to the temperature is large. On the other hand, when the temperature characteristic is good (corresponding to characteristic B in the figure), the change in luminous efficiency (luminance) is small with respect to the temperature change of the phosphor. That is, it means that the gradient of the luminance change with respect to the temperature change is small.

  In CCFL, electrodes are arranged at both ends of a tube, and high-frequency high voltage (up to 50kHz, 1kV) is applied to the electrodes. In CCFL, this electrode part is used as a heat source, and the tube temperature decreases from both ends toward the center of the tube. The distribution of the tube temperature differs depending on the CCFL tube length and the situation when incorporated in the backlight unit, but has a distribution shown in FIG. Luminance / chromaticity distribution is generated by the tube temperature distribution and the temperature characteristics of the phosphor. For example, in the case of a green phosphor having the characteristic A shown in FIG. 6, the luminance is high near an electrode having a high temperature in CCFL, and the luminance is low in a portion having a low temperature. This produces a luminance distribution in the tube axis direction. Furthermore, in the current general-purpose CCFL, the phosphors of three colors are mixed so as to have a predetermined whiteness, so that the green phosphor has high luminance and white with a large amount of green component in the vicinity of the electrode having a high temperature. On the other hand, in the portion where the temperature is low, the brightness of the green phosphor is low, and the white color with a small green component is obtained.

  Further, when the CCFL is arranged in the backlight unit, a temperature distribution is generated in the unit, so that it can be expected that a luminance / chromaticity distribution of the CCFL also occurs. Considering the air convection in the unit in particular, it can be expected that the temperature will rise at the top of the unit. Therefore, it is necessary to sufficiently consider the temperature characteristics of the phosphor. Ideally, a phosphor having a small luminance change in the temperature distribution range of the light source is desired as shown by the characteristic B in FIG.

The temperature characteristics of the phosphor are affected by the phosphor composition ratio. In particular, Ce contained in (La, Tb, Ce) PO ₄ is known as a factor that greatly affects the temperature characteristics, and it is generally said that the temperature characteristics deteriorate as the Ce content increases. Therefore, even if the Ce + Tb amount and the Ce / Tb ratio are optimized for the purpose of increasing the brightness, there is a concern that the temperature characteristics deteriorate due to an increase in the Ce amount. Therefore, the present inventors evaluated the temperature characteristics of (La _1-xy , Tb _x , Ce _y ) PO ₄ in which the composition ratio was changed in the composition range where high luminance can be expected. As a matter of course, since the temperature characteristics vary depending on the wavelength of the excitation source, the temperature characteristics under vacuum ultraviolet light and ultraviolet light excitation (VUV excitation) were evaluated.

  FIG. 4 shows the evaluation results of the temperature characteristics. The horizontal axis is x + y (Ce + Tb amount). The vertical axis represents the luminance change rate, and is a value calculated from the luminance change amount per unit from 50 ° C. to 120 ° C. in consideration of CCFL tube temperature distribution. From the examination so far, it is said that there is no visual problem below the broken line (3% or less) in FIG. From this figure, it was found that there was no problem in temperature characteristics within the range of the composition described above. However, looking at the change due to VUV excitation in FIG. 4, the amount of change in luminance increases with an increase in x + y, and it can be predicted that a problem will occur visually in the range exceeding the above composition.

From the above, the composition ratio of green phosphor (La _1-xy , Tb _x , Ce _y ) PO ₄ used for the light source of the liquid crystal display device is 0.500 <x + y <0.700 and 1.20 <y / x <2.00. It is desirable to reconcile relationships. Furthermore, it is desirable to satisfy both the relationships of 0.500 <x + y <0.650 and 1.50 <y / x <1.70. As a result, it is possible to solve both the problems of high luminance and uniform luminance / chromaticity distribution as the light source of the liquid crystal display device.

The particle diameter of the phosphor in the present invention is preferably such that the median diameter d ₅₀ is in the range of 3.0 μm to 6.0 μm. A phosphor having a particle size larger than this particle size, or a phosphor having a smaller particle size, does not exhibit the effective optical characteristics described above. The median diameter described here is the particle diameter when the mass accounts for 50% or more of the weight of the total powder in the particle size distribution of the phosphor particles.

Such a phosphor is desirably used as a light source of a liquid crystal display device. Then, next, the light source of a liquid crystal display device is described. Currently, CCFL is the main light source, but in recent years, various other light sources have been proposed. Also in these light sources, by using (La _1-xy , Tb _x , Ce _y ) PO ₄ having the composition ratio proposed in the present invention, it is possible to achieve high luminance and uniform luminance / chromaticity distribution. Hereinafter, CCFL (cold cathode tube), HCFL (H ot C athode F luorescent L amp: a hot cathode fluorescent lamp), EEFL (E xternal E lectrode F luorescent L amp: external electrode tube), and the structure and characteristics of the planar light source, The effectiveness of using this phosphor will be described.

<CCFL>
CCFL has the structure shown in FIG. That is, the glass tube 11 has a phosphor 12 and a discharge medium 14 is enclosed inside the tube. The electrodes 13 are disposed at both ends of the tube and are disposed inside the tube. As a discharge medium, mercury is the main component and other rare gases such as argon and neon are also enclosed.

  As already mentioned above, CCFL has a small tube diameter of about 3 to 5 mm, so 185 nm vacuum ultraviolet rays are also emitted from mercury at the same time in addition to 254 nm ultraviolet rays. The influence of ultraviolet excitation is large. Therefore, it is effective to use a green phosphor having the above composition that can achieve both the luminance under vacuum ultraviolet excitation and the luminance under 254 nm ultraviolet excitation.

<HCFL>
In addition to CCFL, hot cathode tube as a light source (HCFL: H ot C athode F luorescent L amp) utilizing, having a composition ratio as described above _{(La 1-xy, Tb x} , Ce y) PO 4 May be used. As shown in FIG. 10, HCFL has a structure similar to CCFL, and is greatly different in that the metal electrode portion 13 is a filament electrode. When a voltage is applied between both electrodes of the HCFL, thermoelectrons are emitted from the filament, and the thermoelectrons excite mercury and emit ultraviolet rays. Similarly to CCFL, HCFL emits 185 nm vacuum ultraviolet light in addition to 254 nm ultraviolet light when the tube diameter is very small. Therefore, it is effective to use a green phosphor having the above composition that can achieve both the luminance under vacuum ultraviolet excitation and the luminance under 254 nm ultraviolet excitation.

<EEFL>
EEFL has a structure shown in FIG. The structure is similar to CCFL, and is a structure in which a fluorescent material 12 is provided on a glass tube 11. However, the electrodes 13 are different from the CCFL in that they are arranged at both ends of the tube and arranged outside the tube. In EEFL, a high voltage is applied to an external electrode to excite mercury in the tube by an induced electric field, and a phosphor is caused to emit light by ultraviolet light having a wavelength of 254 nm and vacuum ultraviolet light having a wavelength of 185 nm emitted from the mercury.

  In EEFL, the glass tube directly under the electrode serves as a dielectric layer, and heat is generated more than CCFL due to energy loss in the dielectric layer. The temperature at the electrode end is higher than the temperature at the CCFL end. This causes a temperature distribution in the tube axis direction, resulting in a luminance distribution and a chromaticity distribution higher than the CCFL. Therefore, by using the green phosphor having the above composition ratio, it is possible to simultaneously achieve high luminance of EEFL and uniform luminance / chromaticity distribution.

<Plane light source>
The planar light source has a structure shown in FIG. That is, it has the structure comprised from the airtight container 15 (back glass 15A, front glass 15B) provided with the fluorescent substance 12, and the electrode 13 (13A, 13B) arrange | positioned on the back glass. Further, a dielectric 16 is disposed on the electrode. The discharge medium 14 is enclosed in the sealed container. The discharge medium varies depending on the type of the planar light source, but there is also a light source that uses mercury.

  In this case, since 254 nm ultraviolet rays and 185 nm vacuum ultraviolet rays are emitted in the same manner as CCFL, it is effective to use a green phosphor having the above composition ratio. In particular, in a flat light source for a large-sized liquid crystal display device, the use of this phosphor is effective because its surface is wide and temperature distribution is likely to occur within the surface.

  In addition, even with other light sources, in the case of a light source that excites the phosphor by vacuum ultraviolet light having a wavelength of less than 200 nm and ultraviolet light having a wavelength of 200 nm or more, the green phosphor having the composition shown in the present invention is used. It is effective to use. As a result, high luminance and uniform luminance / chromaticity distribution can be achieved at the same time. By using a backlight including such a light source, a high-quality and low-cost liquid crystal display device with high brightness and suppressed brightness / chromaticity distribution can be obtained.

  Furthermore, a light source including such a green phosphor is particularly effective in combination with a VA mode liquid crystal element. Liquid crystal elements are classified into various modes according to the initial alignment state of the liquid crystal molecules and the driving method thereof, and currently IPS mode, VA mode, OCB mode, and TN mode are representative. Although the present invention can be used for all modes, the disadvantage of the VA mode liquid crystal element can be improved by combining with the VA mode liquid crystal element. The reason will be described below.

  As shown in FIG. 14, the VA mode liquid crystal element includes a pair of substrates 31 (31A, 31B) facing each other, an alignment film 33 applied on the inner surface of the substrates, and a liquid crystal 34 sandwiched between the alignment films. Consists of Further, polarizing plates 32 (32A and 32B) are disposed outside the substrate. The alignment film 33 is a vertical alignment film. The electrodes 37 (37A, 37B) are formed on both substrates, and a voltage is applied between these electrodes. When no voltage is applied, the long axis direction of the liquid crystal is in a direction substantially perpendicular to the substrate surface (FIG. 14A). At this time, the display of the liquid crystal display device is off, that is, black display. Next, when a voltage is applied to the electrode, an electric field in a direction substantially perpendicular to the substrate surface is generated. By tilting the liquid crystal molecules to the substrate surface by this electric field, the refractive index of the liquid crystal layer is changed, and Adjust the light intensity. FIG. 14B shows this state, and the liquid crystal display device is in a display-on state.

  This VA mode has a drawback specific to the VA mode in that the chromaticity greatly changes depending on the viewing angle. In particular, the change in chromaticity in the halftone display is large. Therefore, in the VA mode liquid crystal display device, the image quality is greatly reduced as compared with other display modes due to the synergistic effect of the chromaticity change of the light source and the chromaticity change caused by the liquid crystal element. In particular, when viewing both screen ends of a large-screen VA mode liquid crystal display device, the chromaticity change is the largest due to the synergistic effect of the chromaticity change near the CCFL electrode and the chromaticity change with respect to the viewing angle of the liquid crystal element.

Therefore, by using (La, Tb, Ce) PO ₄ having the above composition ratio with good temperature characteristics as a green phosphor, it is possible to suppress the change in chromaticity of CCFL and to improve the chromaticity in a VA mode liquid crystal display device. The viewing angle dependency can be reduced. That is, a large VA mode liquid crystal display device with high image quality can be obtained.

Hereinafter, detailed examples will be described. However, the present invention is not limited to the following examples. In addition, a liquid crystal equipped with a light source produced using a green phosphor (La _1-xy , Tb _x , Ce _y ) PO ₄ (x + y = 0.428, y / x = 2.18), which has been conventionally used in CCFLs. The display device will be described in Comparative Example 1.

<Example 1>
The composition ratio of the green phosphor (La _1-xy , Tb _x , Ce _y ) PO ₄ used in this example is x + y = 0.602 and y / x = 1.68. This phosphor has higher brightness than the green phosphor used in Comparative Example 1 at room temperature. The luminance is 109% with a wavelength of 254 nm excitation and 102% with a vacuum ultraviolet excitation (VUV excitation). FIG. 1 shows the temperature characteristics of the phosphor. FIG. 1 (a) shows the characteristics when excited with ultraviolet light having a wavelength of 254 nm.

  FIG. 1B shows the temperature characteristics under vacuum ultraviolet excitation. It can be seen that the luminance change is small in the light source temperature distribution range. Accordingly, it is possible to achieve both the emission characteristics of the wavelength 254 nm ultraviolet excitation and the vacuum ultraviolet excitation (VUV excitation), and high brightness and uniform brightness / chromaticity distribution in the CCFL can be expected.

  The liquid crystal display device according to this embodiment includes a backlight unit 1 and a liquid crystal element 2 as shown in FIG. Further, the backlight unit 1 includes a white light source 5 and a drive circuit 9 (inverter) for lighting the light source 5, a housing 3, a reflection plate 4, a diffusion plate 6, a prism sheet 7, and a polarization reflection plate 8.

In this embodiment, the CCFL shown in FIG. 9 is used as a white light source, and only the composition ratio of the green phosphor material (La _1-xy , Tb _x , Ce _y ) PO ₄ used for the white light source is different from the conventional one. Hereinafter, the production of CCFL using a green phosphor having a new composition and the production of an IPS mode liquid crystal display device using the CCFL will be described.
(1) CCFL production:
The outline of the CCFL production procedure is as shown in FIG. First, a binder such as alumina and each color phosphor material are mixed in an organic solvent composed of nitrocellulose and butyl acetate called a vehicle. This liquid mixture is called a suspension. The green phosphor uses (La _1-xy , Tb _x , Ce _y ) PO ₄ (x + y = 0.602, y / x = 1.68), and the blue phosphor and the red phosphor are the same BaMgAl as before. ₁₀ O ₁₇ : Eu ²⁺ and Y ₂ O ₃ : Eu ³⁺ are used.

Next, one side of the previously cleaned glass tube is dipped in this suspension, sucked with a pump from the other side, and the suspension is pulled up to apply the phosphor to the inner wall of the glass tube. The material of the glass tube is copal glass, and the tube diameter is 3 mm. Then, the glass tube is baked (fired) to fix the phosphor to the inner wall of the tube. Then, an electrode is attached and the one side of a glass tube is sealed. A gas pressure is adjusted by injecting and exhausting a rare gas such as argon Ar or neon Ne from the opposite side of the sealed side. Furthermore, after injecting mercury, the glass tube is sealed. Finally, the glass tube is turned on for a predetermined time to perform an aging process.
(2) Backlight unit assembly:
Next, the assembly of the backlight unit will be described with reference to FIG. The plurality of completed CCFLs 5 are arranged in the metal casing 3. In a liquid crystal display device such as a liquid crystal television that requires high brightness, a direct system in which a plurality of CCFLs are arranged in a plane is adopted.

Between the metal housing 3 and the CCFL 5, a reflector 4 for efficiently using light emitted from the CCFL toward the housing is disposed. Further, in order to suppress the luminance in-plane distribution of the liquid crystal display device, a diffusion plate 6 is disposed immediately above the CCFL. Furthermore, a prism sheet 7 and a polarizing reflector 8 are arranged for the purpose of improving the luminance of the liquid crystal display device. An inverter 9 is connected to the CCFL, and the lighting control of the CCFL is performed by driving the inverter. These are collectively referred to as the backlight unit 1.
(3) Liquid crystal element:
Directly above the backlight unit 1, a liquid crystal element 2 having a color filter that adjusts the amount of light transmitted from the backlight (white light source CCFL) and separates light into red, green, and blue for each pixel is disposed.

A schematic cross-sectional view of the liquid crystal element is as shown in FIG. As the substrate 21, a glass substrate with a normal thickness of 0.5 mm is used. On one of the substrates 21A, an electrode (not shown in FIG. 13) is formed for each pixel, also the thin film transistor for supplying a voltage to the electrodes: forming a (TFT T hin F ilm T ransistor ). On the other substrate 21B, a color filter 25 (red 25A, green 25B, blue 25C) is formed for each pixel. An alignment film 23 for aligning liquid crystal molecules is formed on the surfaces of the pair of substrates, and a liquid crystal 24 is sandwiched between the substrates. Further, polarizing plates 22 (22A and 22B) are disposed outside the substrate.

  Finally, the backlight unit 1 and the liquid crystal element 2 are combined and covered with the housing 10 to obtain a liquid crystal display device.

  According to this embodiment, it is possible to achieve both high brightness of CCFL and uniform brightness / chromaticity distribution. Further, by using such a light source, a high-quality liquid crystal display device that achieves both low cost and high image quality can be obtained.

<Example 2>
This example differs from Example 1 only in the composition ratio of the green phosphor (La _1-xy , Tb _x , Ce _y ) PO _{4 used} . The composition ratio is x + y = 0.551, y / x = 1.68. The rest is the same as in the first embodiment.

  This phosphor has higher brightness than the green phosphor used in Comparative Example 1 at room temperature. The luminance is 107% with a wavelength of 254 nm excitation and 102% with vacuum ultraviolet excitation (VUV excitation).

  1A and 1B show temperature characteristics of the phosphor. It can be seen that the luminance change is small in the light source temperature distribution range for both the wavelength 254 nm ultraviolet excitation and the vacuum ultraviolet excitation (VUV excitation). Accordingly, it is possible to achieve both the emission characteristics of 254 nm ultraviolet excitation and vacuum ultraviolet excitation, and high brightness and uniform luminance and chromaticity distribution can be expected in CCFL.

  According to this embodiment, it is possible to achieve both the improvement of CCFL luminance and the uniform luminance distribution and chromaticity distribution. Further, by using such a light source, a high-quality liquid crystal display device that achieves both low cost and high image quality can be obtained.

<Example 3>
This example differs from Example 1 only in the composition ratio of the green phosphor (La _1-xy , Tb _x , Ce _y ) PO _{4 used} . The composition ratios are x + y = 0.505 and y / x = 1.70. The rest is the same as in the first embodiment.

  This phosphor has higher brightness than the green phosphor used in Comparative Example 1 at room temperature. The luminance is 105% with excitation at a wavelength of 254 nm and 103% with vacuum ultraviolet excitation (VUV excitation). 1A and 1B show temperature characteristics of the phosphor. It can be seen that both the 254 nm ultraviolet excitation and the vacuum ultraviolet excitation exhibit small changes in luminance in the light source temperature distribution range. Therefore, the light emission characteristics of 254 nm ultraviolet excitation and vacuum ultraviolet excitation are compatible, and high brightness and uniform brightness / chromaticity distribution can be expected in CCFL.

  According to this embodiment, it is possible to achieve both the improvement of CCFL luminance and the uniform luminance distribution and chromaticity distribution. Further, by using such a light source, a high-quality liquid crystal display device that achieves both low cost and high image quality can be obtained.

<Example 4>
This embodiment differs from the first embodiment in the type of light source. In the first embodiment, CCFL is used, but in this embodiment, EEFL shown in FIG. 11 is used. The phosphor used for EEFL is the same as in Example 1.

  Production of EEFL differs from CCFL in the formation of electrode parts. In EEFL, after applying a phosphor to a glass tube, one side of the glass tube is sealed and evacuated, then mercury as a discharge medium is introduced and the other side of the glass tube is sealed. Thereafter, a flexible electrode such as a copper tape is disposed outside the glass tube.

  In such an EEFL, since the glass tube itself serves as a capacitor, a ballast capacitor is not required, and multiple lighting driving in which a plurality of lamps 5 are lit by a single inverter 9 is possible. This can be expected to reduce costs because the number of inverters can be greatly reduced compared to CCFL.

  However, in this EEFL, the glass tube itself becomes a dielectric, and the calorific value is larger than that of CCFL. That is, the temperature rises very much at the electrode part. Accordingly, a temperature distribution is more likely to occur than CCFL, and a luminance / chromaticity distribution due to the temperature characteristics of the phosphor is likely to occur. Therefore, by using this phosphor, it is possible to simultaneously achieve high luminance and uniform luminance / chromaticity distribution.

  The liquid crystal element 2 and the like are the same as those in the first embodiment. According to this embodiment, it is possible to achieve both the improvement of the luminance of EEFL and the uniformization of the luminance distribution and the chromaticity distribution. In addition, by using such a light source, a high-quality liquid crystal display device that achieves both low cost and high image quality can be obtained.

<Example 5>
The present embodiment is different from the first embodiment in the configuration of the liquid crystal element 2 to be used. In the first embodiment, an IPS mode liquid crystal element is used. In this embodiment, a VA mode liquid crystal element is used.

  In the conventional VA mode liquid crystal display device, the viewing angle dependency of the chromaticity change is large, and when the screen is viewed from the front, the chromaticity change on both sides of the screen is a big problem. However, by using this phosphor to suppress changes in CCFL brightness and chromaticity, it is possible to suppress changes in brightness and chromaticity on both sides of the screen compared to conventional VA mode liquid crystal display devices. It becomes. In particular, a change in chromaticity in halftone display can be suppressed.

<Comparative Example 1>
This comparative example is a conventional technique for comparison with the above-described example, and (La _1-xy , Tb _x , Ce _y ) PO ₄ (x + y = 0.428, y / x = 2.18). Others are the same as in the first embodiment.

  This phosphor is a standard for luminance, and at room temperature, the luminance is 100% with wavelength excitation of 254 nm and vacuum ultraviolet excitation (VUV excitation). 1A and 1B show temperature characteristics of the phosphor. In particular, it can be seen that the luminance change is large in the light source temperature distribution range when the wavelength is 254 nm.

It is a figure which shows the temperature characteristic by wavelength 254nm excitation of a green fluorescent substance. It is a figure which shows the temperature characteristic by VUV excitation of a green fluorescent substance. It is a figure which shows the composition ratio x + y (Ce + Tb amount) dependence of green phosphor relative luminance. It is a figure which shows the composition ratio y / x (Ce / Tb ratio) dependence of green fluorescent substance relative luminance. It is a figure which shows the composition ratio x + y (Ce + Tb amount) dependence of the green phosphor luminance change rate. It is a figure which shows the emission spectrum of a green fluorescent substance. It is a figure for demonstrating conceptually the temperature characteristic of fluorescent substance. It is a figure which shows notionally the temperature distribution in a CCFL pipe-axis direction. It is a figure which shows the disassembled perspective view of a liquid crystal display device. It is a figure which shows the outline of the cross-section of a cold cathode tube (CCFL). It is a figure which shows the outline of the cross-section of a hot cathode tube (HCFL). It is a figure which shows the outline of the cross-section of an external electrode tube (EEFL). It is a figure which shows the schematic cross section of a planar light source. It is a figure which shows the outline of the cross-section of a liquid crystal element. It is a figure for demonstrating the outline of the liquid crystal element of VA mode. It is a figure which shows the preparation flow of a cold cathode tube (CCFL).

Explanation of symbols

1 ... Backlight unit,
2 ... Liquid crystal element,
3 ... Case (bottom),
4 ... reflector,
5 ... Light source (eg CCFL),
6 ... diffusion plate,
7 ... Prism sheet,
8 ... Polarizing reflector,
9 ... Inverter,
10: Housing (top),
11 ... Glass tube,
12 ... phosphor,
13 ... electrodes
14 ... discharge medium,
15 ... Sealed container (15A, 15B),
16 ... partition wall,
21, 31 ... Glass substrate,
22, 32 ... Polarizing plate,
23, 33 ... alignment film,
24, 34 ... Liquid crystal,
25 (25A, 25B, 25C) ... color filters (red, green, blue),
26 ... spacer,
27, 37: Pixel electrodes.

Claims (13)

A blue phosphor whose emission color is blue,
A green phosphor that is green,
A light source having a three-color phosphor with a red phosphor that is red;
A liquid crystal display device comprising: a liquid crystal element having a color filter that adjusts a transmission amount of light from the light source for each pixel and transmits blue, green, or red light for each pixel;
The green phosphor, the composition formula _{(La 1-x-y,} Tb x, Ce y) is represented by PO _4,
The composition ratios x and y satisfy the following equations (1) and (2) respectively ,
The light source is
A sealed container comprising the blue phosphor, the green phosphor and the red phosphor;
A discharge medium enclosed in the sealed container;
An electrode provided in a sealed container for applying a voltage to the discharge medium,
Exciting the phosphor with a plurality of ultraviolet rays having different wavelengths emitted from the discharge medium to emit light,
The main component of the discharge medium is mercury Hg,
Among the ultraviolet rays emitted from the discharge medium, one includes vacuum ultraviolet rays having a wavelength of 185 nm, and the other includes ultraviolet rays having a wavelength of 254 nm,
The intensity ratio I ₁₈₅ / I ₂₅₄ between the vacuum ultraviolet ray having a wavelength of 185 nm and the ultraviolet ray having a wavelength of 254 nm is 0.20 or more in a sealed container,
The sealed container is a tubular glass tube,
The liquid crystal display device internal diameter of the tube, characterized in der Rukoto below 5 mm.
0.500 <x + y <0.700 (1)
1.20 <y / x <2.00 (2) A blue phosphor whose emission color is blue,
A green phosphor that is green,
A light source having a three-color phosphor with a red phosphor that is red;
A liquid crystal display device comprising: a liquid crystal element having a color filter that adjusts a transmission amount of light from the light source for each pixel and transmits blue, green, or red light for each pixel;
The green phosphor, the composition formula _{(La 1-x-y,} Tb x, Ce y) is represented by PO _4,
The composition ratios x and y satisfy the following equations (3) and (4) respectively ,
The light source is
A sealed container comprising the blue phosphor, the green phosphor and the red phosphor;
A discharge medium enclosed in the sealed container;
An electrode provided in a sealed container for applying a voltage to the discharge medium,
Exciting the phosphor with a plurality of ultraviolet rays having different wavelengths emitted from the discharge medium to emit light,
The main component of the discharge medium is mercury Hg,
Among the ultraviolet rays emitted from the discharge medium, one includes vacuum ultraviolet rays having a wavelength of 185 nm, and the other includes ultraviolet rays having a wavelength of 254 nm,
The intensity ratio I ₁₈₅ / I ₂₅₄ between the vacuum ultraviolet ray having a wavelength of 185 nm and the ultraviolet ray having a wavelength of 254 nm is 0.20 or more in a sealed container,
The sealed container is a tubular glass tube,
A liquid crystal display device having an inner diameter of a tube of 5 mm or less .
0.500 <x + y <0.650 (3)
1.50 <y / x <1.70 (4) The electrodes provided in the glass tube are disposed at both ends of the glass tube,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is disposed inside the glass tube . The electrodes provided in the glass tube are disposed at both ends of the glass tube,
The liquid crystal display device according to claim 1 , wherein the liquid crystal display device is disposed outside the glass tube . The light source has mercury Hg as a main component of the discharge medium ,
The liquid crystal display device according to claim 1 , wherein the tube is a cold cathode fluorescent tube having an inner diameter of 5 mm or less . 2. The liquid crystal display device according to claim 1 , wherein the green phosphor has a median particle size d _{50 in} the range of 3.0 μm to 6.0 μm . The electrodes provided in the glass tube are disposed at both ends of the glass tube,
The liquid crystal display device according to claim 2 , wherein the liquid crystal display device is disposed inside the glass tube. The electrodes provided in the glass tube are disposed at both ends of the glass tube,
And a liquid crystal display device according to claim 2, characterized in that it is arranged on the outer portion of the glass tube. The light source has mercury Hg as a main component of the discharge medium,
3. The liquid crystal display device according to claim 2 , wherein the tube is a cold cathode fluorescent tube having an inner diameter of 5 mm or less . 3. The liquid crystal display device according to claim 2 , wherein the green phosphor has a median particle diameter d _{50 in} a range of 3.0 μm to 6.0 μm . The liquid crystal element is
A pair of opposing transparent substrates;
An alignment film coated on the inner surfaces of the pair of substrates;
A liquid crystal layer sandwiched between the alignment films;
A polarizing plate disposed on the outside of the pair of substrates,
The alignment film is a vertical alignment film;
The liquid crystal is aligned substantially perpendicular to the substrate surface when no voltage is applied,
2. The liquid crystal display device according to claim 1, wherein the amount of transmitted light is adjusted by inclining with respect to the substrate surface when a voltage is applied . The liquid crystal element is
A pair of opposing transparent substrates;
An alignment film coated on the inner surfaces of the pair of substrates;
A liquid crystal layer sandwiched between the alignment films;
A polarizing plate disposed on the outside of the pair of substrates,
The alignment film is a vertical alignment film;
The liquid crystal is aligned substantially perpendicular to the substrate surface when no voltage is applied,
3. The liquid crystal display device according to claim 2, wherein the amount of transmitted light is adjusted by inclining with respect to the substrate surface when a voltage is applied . A blue phosphor whose emission color is blue,
A green phosphor that is green,
A light source having a three-color phosphor with a red phosphor that is red;
A liquid crystal display device comprising: a liquid crystal element having a color filter that adjusts a transmission amount of light from the light source for each pixel and transmits blue, green, or red light for each pixel;
The green phosphor, the composition formula _{(La 1-x-y,} Tb x, Ce y) is represented by PO _4,
The composition ratios x and y satisfy the following equations (3) and (4) respectively,
0.500 <x + y <0.650 (3)
1.50 <y / x <1.70 (4)
The light source is
A sealed container comprising the blue phosphor, the green phosphor and the red phosphor;
A discharge medium enclosed in the sealed container;
An electrode provided in a sealed container for applying a voltage to the discharge medium,
Exciting the phosphor with a plurality of ultraviolet rays having different wavelengths emitted from the discharge medium to emit light,
The main component of the discharge medium is mercury Hg,
Among the ultraviolet rays emitted from the discharge medium, one includes vacuum ultraviolet rays having a wavelength of 185 nm, and the other includes ultraviolet rays having a wavelength of 254 nm,
The intensity ratio I ₁₈₅ / I ₂₅₄ between the vacuum ultraviolet ray having a wavelength of 185 nm and the ultraviolet ray having a wavelength of 254 nm is 0.20 or more in a sealed container,
The sealed container is a tubular glass tube,
The inner diameter of the tube is 5 mm or less,
The liquid crystal element is
A pair of opposing transparent substrates;
An alignment film coated on the inner surfaces of the pair of substrates;
A liquid crystal layer sandwiched between the alignment films;
A polarizing plate disposed on the outside of the pair of substrates,
Liquid crystal display device includes a liquid crystal display mode you and drives the IPS mode.

Images